An upper level trough over Washington and Oregon brings snow to north-central Idaho.
Every event with a place to put it; 2 filed by county or forecast zone are drawn at its center, in a lighter ring. Tap one for its entry below.
Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The episode as NWS MSO wrote it up.
An upper level trough over Washington and Oregon brings snow to north-central Idaho.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS Missoula, MT wrote its last area forecast discussion before the first event at Dec 23, 2:59 AM PST, 1 hour 1 minute earlier.
Area Forecast Discussion National Weather Service Missoula MT 359 AM MST Sun Dec 23 2012 ..Potential holiday travel impacts due to snow on Christmas Eve... .DISCUSSION...A small disturbance visible on satellite and radar moving through central Idaho this morning will cause scattered snow showers this morning. Cancelled the advisories for Lolo pass and the area near Clearwater Junction on Highway 200 this morning since the main front is through the area and remaining snow showers have been light and brief. Even though the snow has decreased, drivers should still use caution as roads may still be slick. By this afternoon the showers should be confined to the mountains providing a short break for most of the populated areas. Tonight an approaching system will cause surface pressure to lower and help draw in a cold airmass from east of the Continental Divide. This will cause windy conditions overnight in areas prone to strong east winds, like Bad Rock canyon. Recent model forecasts have changed significantly by drawing more cold air into northwest Montana and potentially setting up a wide band of moderate snow early Monday morning. Since this is such a recent change, the placement of the wide band of snow is uncertain but looks to lining up near Missoula. This brings with it the potential for 3 to 4 inches of snow in a few hours in Missoula Monday morning. Those planning to travel Monday should be prepared difficult travel along Interstate 90, in and around Missoula, and along the portions of Highway 93 near Interstate 90. Gusty east winds will continue to be present through Monday night, continuing to transport cold air westward across western Montana. Sub-zero temperatures are likely for valleys along and west of the Continental Divide on Tuesday morning. Following a brief respite from snowy conditions during Tuesday, the next storm system will arrive over the Northern Rockies Tuesday night. Model guidances depict widespread precipitation all the way through Friday, however snow amounts will be fairly minor within any given 6-hour period. Travel impacts will be mainly over the mountain passes due to ice and snow covered roads. Otherwise, relatively cool December temperatures will be present. After Friday, a lot of uncertainty and noise are introduced to model guidances. Large amounts of variability exist among each model during this time. Considering these unclear projections, a forecast trended toward climatology continues to be favored at this time. && .AVIATION...Scattered showers associated with a passing short wave will impact area terminals this morning with periods of reduced visibility in snow and lower ceilings. KMSO and KGPI will have the most frequent impacts. The showers will decrease this afternoon under the influence of a shortwave ridge. Orographic lift and moist southwest flow keep the showers going over the mountains and maintain partial mountain obscurations throughout the day. An approaching trough will cause showers to increase again this evening. Surface low pressure associated with this system will help draw a strong polar airmass east of the Continental Divide into the area causing strong northeast winds at KGPI overnight. Recent model runs indicate a broad surface trough along the edge of the cold air lining up to potentially cause overrunning and moderate to heavy snow late Sunday night near KMSO. This feature is a significant change from recent forecasts and should be monitored closely for changes to the forecast as confidence grows in the timing and placement could significantly affect KBTM, KMSO, KGPI late tonight. && .MSO WATCHES/WARNINGS/ADVISORIES... MT...None. ID...None. && Follow us on Facebook and Twitter! https://www.facebook.com/US.NationalWeatherService.Missoula.gov https://www.twitter.com/NWSMissoula
The national radar mosaic for the moment the first event began.
2 heavy snow. Local standard time, as filed.
A trained spotter located in Weippe measured 9 inches of snow.
A COOP observer in Pierce reported 7.4 inches of snow.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Idaho in 2012Every state in 2012This day in weather historyWarnings in Idaho, December 2012
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 424874, 424877.